This invention relates to a locking apparatus for a sliding door slidable in a groove, particularly to a locking apparatus comprising an overriding safety lock for preventing the sliding door from being illegally unlocked.
Sliding doors, particularly automatic sliding doors, are popularly mounted on the doorways of supermarkets, shops, etc. The structure of the prior art of the locking apparatus for the sliding door will be described hereinafter by making reference to accompanying FIG. 6-10. Sliding doors usually comprise two leaves which are slidable in a groove, each of the leaves being formed with a rectangular aluminum frame and a glass panel secured therein. The locking apparatus of the sliding door comprises a hooking assembly (q) and a hook-retaining block (g). The hooking assembly (q) comprises two vertical pieces (a), (a') and is mounted at the vertical inner frame (r) of the first leaf (s) of the sliding door. As the sliding door is shut, the inner frame (r) of the first leaf (s) meets the corresponding inner frame of the second leaf (not shown) thereof. The hook-retaining block (g) is mounted at the end face of the inner frame of the second leaf of the sliding door so as to contact with the corresponding hooking assembly (q) at the first leaf (s). Both the first and second vertical pieces (a'), (a) of the hooking assembly (q) are plate means in which the upper front portions are provided with a vertical lengthwise recess. The lengthwise recess is used for manual pulling of the first leaf (s) of the sliding door from both sides thereof. The lower portion of the first vertical piece (a') is provided with a conventional lock (h) which is controllable with a key means. As the key means (not shown) is used to lock or unlock the lock (h), the post (i), projecting rearwards, rotates accordingly. Since the first and second vertical pieces (a' and a) are mounted together oppositely and in parallel through the side frame (r) (see FIG. 7), the vertically slidable locking block (d) is controllable by the rotating post (i) via a triangular hole (j) provided on the slidable locking block (d). A hook element (f) corresponding to the hook-retaining block (g) is secured to the vertically slidable block (d). As the lock (h) is locked by a key means so as to lower the slidable block (d) or as the slidable block (d) is directly lowered by pushing downwards the control button (t) provided on the lower front portion of the second vertical piece (a), hook element (f) descends so as to become engaged with the hook-retaining block (g). The sliding door is then locked. Similarly, the sliding block (d) can be directly elevated by pushing the control button (t) upwards or indirectly elevated by unlocking the lock (h) with the key means so as to disengage the hook element (f) from the hook-retaining block (g). Accordingly, the sliding door is unlocked. An overriding safety lock (k) comprises a disc (l) with an outer-projecting rib (p) on its outer face, and an inner-projecting cylindrical post (m) with the middle portion thereof flattened. The middle portion of the inner-projecting cylindrical post (m) is interposed in the vertical slot (o) provided at the upper end (n) of the sliding hooking block (d) when the sliding hooking block (d) is in its top position and the hook element (f) is not in engagement with the hook-retaining block (g). As the sliding block (d) is lowered to its bottom position so as to make the hook element (f) engage with the hook-retaining block (g), the middle portion of the inner-projecting post (m) is around the top end of the vertical slot (o) of the sliding block (d). The two top edges of the slot (o) are rounded. The disc (l) can thus be turned 90 degrees so as to enable the inner-projecting post (m) thereof to block the sliding hooking block (d) from elevating. The engagement between the hooking assembly (q) and the hook-retaining block (g) is hence ensured.
An inherent drawback of the prior art locking apparatus for the sliding door is that the outer-projecting rib (p) of the disc (l) of the overriding safety lock (k) is difficult to manipulate with fingers. The difficulty of the manipulation of the disc (l) of the overriding safety lock (k) reduces the efficiency of the operation thereof. Further, the difficulty of rotating the slightly outer-projecting rib (p) of the disc (k) is significantly harmful to the fingernails, particularly women's long fingernails.